Jeroen Paul Thesseling is my favorite fretless player right now.
He plays all kinds of stuff, jazz, flamenco, world music, and metal.
You check out some of his stuff at his site
http://www.jeroenthesseling.com/
Just click audio.
His Obscura stuff is death metal mixed with all types of other stuff. And the ensemble is a mixture of jazz, flamenco, and world music.